OBJECTIVETo investigate the role of nuclear factor erythroid 2-related factor 2 (Nrf2) as a key transcription factor of cytoprotection against inflammation in the spinal cord upregulation of matrix metalloproteinase-9 (MMP-9), tumor necrosis factor-α(TNF-α) after spinal cord injury (SCI).

METHODSWild-type Nrf2(+/+) and Nrf2(-/-)-deficient mice were subjected to a murine SCI model induced by the application of vascular clips (force of 10 g) to the dura after a three-level T8-T10 laminectomy. The wet/dry weight ratio was used to reflect the percentage of water content of impaired spinal cord tissue at 48 h after SCI. The mRNA levels of MMP-9 were determined using reverse-transcriptase polymerase chain reaction (RT-PCR), and the protein levels of TNF-α and MMP-9 were detected by enzyme-linked immunosorbent assay at 24 h after SCI. Furthermore, gelatin zymography analysis was used to show MMP-9 activity of spinal cord tissue at 24 h after SCI. Software SPSS 16.0 was used for the statistical analysis.

RESULTSAfter SCI, spinal cord water content, the expression of TNF-α and MMP-9 all increased in both injured Nrf2(+/+) and Nrf2(-/-) mice compared with their respective sham-operated mice. However, Nrf2(-/-) mice were shown to have more severe spinal cord edema, more TNF-α expression, more production and activity of MMP-9 compared with their wild-type Nrf2(+/+) counterparts after SCI (P < 0.05).

CONCLUSIONSThe results suggest that Nrf2 plays an important protective role in limiting the spinal cord upregulation of TNF-α and MMP-9 after SCI. It may be a new therapeutic target of SCI.